Molar absorptivity Epsilon of proteins, and other secondary measures of biopolymers in general, have been used without much concern for their basis and precision. As a result, discrepant values have been assigned to a single substance and the validity of values has often become questionable. In order to correct this chaotic situation and provide firm ground for concentration determination, I have proposed a simple, easy-to-follow protocol for dry weight determination of protein solutions, which produced promising results, when tested on ten different proteins. The protocol should be tested on more and different kinds of proteins, including membrane proteins soluble only in detergent solution. In addition, the protocol should be tested on other classes of biopolymers, including polysaccharides, nucleic acids, and their complexes such as glycoproteins, nucleoproteins and viruses. Correlation between the concentration of biopolymers obtained by dry weight and that by other methods, particularly chemical methods such as Lowry's method for proteins, the anthrone reaction for carbohydrates and phosphorus determination for nuclei acids will also be examined. This is particularly important to a method like the Lowry method which is used with an arbitrary standard, in most cases bovine serum albumin, which has a different amino acid composition therefore different color response from those of the protein being determined.